The Rapids needed a significant turnaround after losing the first leg by the same scoreline last Sunday but it was Kansas City, roared on by their home crowd, who performed with urgency and advanced to the conference final with a dominant 4-0 aggregate win.
Graham Zusi free-kicks set up both goals on a rainy evening at Livestrong Sporting Park with defender Aurelien Collin heading home the opener in the first half and rookie CJ Sapong adding the second, also with the head, after halftime.
"Zusi has an amazing foot, every time he [serves] we feel we can score," Collin told reporters. "We did an amazing job today. It was not easy to play against this team in this weather. I'm very proud of my team tonight."
Kansas City played aggressively despite the drizzling rain and forward Sapong set up the first goal with a charging run that resulted in a foul in the 27th minute.
Midfielder Zusi's pinpoint service found Frenchman Collin and his delivery of a second free kick in the 75th minute proved no less accurate, allowing Sapong to put the result beyond doubt.
Aiming to become the first back-to-back MLS Cup Champion since the Houston Dynamo in 2006-2007, Colorado were weakened by injuries to key players and uninspired in defeat.
Sporting will face the winner of the other semi-final between Houston Dynamo and Philadelphia Union for a place in the MLS Cup final.
Real Salt Lake later reached the Western Conference final but not until after the Seattle Sounders had given them a genuine scare with a 2-0 second leg victory.
The Sounders played with desperation, firing shots from all angles and they got reward with second-half goals from Osvaldo Alonso and Lamar Neagle.
In the end, Real's 3-0 win in the first leg proved enough for a 3-2 aggregate victory to set up a meeting with the Los Angeles Galaxy or the New York Red Bulls.
It was a third consecutive year that Seattle's season had ended with a conference semi-final defeat, while Real moved forward in their quest for a second title in three years.
